Bipolar electrosurgical scissors

ABSTRACT

Bipolar electrosurgical scissors are disclosed having a pair of blades joined for relative movement in a scissor-like action between open and closed positions. The blades comprise a tissue contacting surface and first and second spaced apart electrodes extending along the surface. Current flow between the first and second electrodes of each blade and between each blade to promote hemostasis in tissue contacting the surface.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No. 08/399,421, filed Mar. 7, 1995, U.S. Pat. No. 6,179,837.

BACKGROUND OF THE INVENTION

The present invention relates generally to electrosurgical scissors, and more particularly, to bipolar electrosurgical scissors to assist in hemostasis of tissue as it is cut by the scissors.

It is common in many surgical procedures to use surgical scissors for cutting tissue that is vascularized, i.e., contains blood vessels. The resultant bleeding that occurs is not only of concern from the standpoint of blood loss, but the blood may also obscure the surgical field or site. Controlling such bleeding has, in the past, required significant time and attention of the surgeon during many surgical procedures.

In recent years, efforts have been devoted to developing scissors that use radiofrequency (“RF”) energy in a manner such that the tissue is heated as it is cut, to promote immediate hemostasis. Early efforts at such electrosurgial scissors used monopolar RF power, where the scissors constituted one electrode, and the patient rested on the other electrode, which was typically in the form of a conductive mat, to complete the circuit. Current flowed generally through the patient between the electrodes due to a voltage applied across the electrodes by an RF power supply.

Monopolar applications, however, had certain drawbacks. Inadvertent contact between the scissors and other tissue could result in unwanted tissue damage. In addition, the flow of current through the body of the patient could take uncertain or unpredictable paths with potential unwanted injury to other tissue.

More recently, efforts have been made to develop bipolar electrosurgical scissors to overcome the drawbacks with monopolar scissors. Specifically, efforts have been made to develop scissors in which one blade includes one electrode and the other blade includes the other electrode, so that current flows between the blades as they cut the desired tissue.

Example of recent efforts to develop bipolar scissors are found in U.S. Pat. Nos. 5,324,289 and 5,330,471. These patents disclose bipolar scissors in which one blade of the scissors has one electrode, and the other blade of the scissors has the other electrode, so that current flows between the blades as they come into proximity during cutting. Various embodiments of bipolar scissors are disclosed in these patents, but typically a layer of insulating material is provided on at least one shearing surface of one of the blades, and the hinge pin or fastener which pivotally connects the blades is electrically insulated, so that the electrically active parts of the scissor blades do not contact each other during operation of the instrument. With the construction as shown in these patents, the electrical current flows between the blades at a point just forward of where the shearing surfaces actually touch. The current flow between the blades causes a heating of the tissue and promotes local coagulation and hemostasis during the cutting procedure.

In U.S. Pat. No. 5,352,222, bipolar scissors are shown in which each blade of the scissors is a laminated assembly of a metal shearing surface, a metal blade support and intermediate layer of insulating material. The blade support of one blade acts as one electrode, and the blade support of the other blade acts as the other electrode, so that electrical energy flows between the blade supports as the blades close on the tissue being cut. A short circuit between the shearing surface is prevented by reason of the insulating layer between the metal shearing surface and the blade support. This scissor construction is purported to be more economical to manufacture than the blade structure disclosed in U.S. Pat. Nos. 5,324,289 and 5,330,471. However, because the shearing surface is a separate piece, bonded to the blade support, a particularly high strength and high precision epoxy bonding process is required in the '222 patent so that the shearing surface remains attached to the blade support despite the shearing forces exerted upon it during repeated cutting.

What the above patents have in common, is that each blade forms one of the electrodes attached to a bipolar RF energy source, so that the only current that flows is between the blades as they close. Although the bipolar scissors described in the above-identified patents are believed to be an advance over the earlier monopolar scissors, they typically required the electrically active parts of the blades to be insulated from one another, which tends to complicate the design and materials of the blade actuating mechanism. Accordingly, development work continues to provide bipolar scissors which are easy to use, more economic to make, versatile and/or which are effective in promoting hemostasis during cutting of various tissues, particularly including tissues that are highly vascularized.

SUMMARY OF INVENTION

In accordance with the present invention, tissue cutting apparatus, such as scissors, may be provided in which each cutting blade itself includes two electrodes for connection to a bipolar RF energy power supply. More specifically, the tissue cutting apparatus of the present invention comprises a pair of blades joined for relative movement in a scissor-like action between open and closed positions. Each of the blades has a tissue contacting surface for contacting the tissue therebetween as the blades close during the cutting action. The tissue contacting surface of at least one and preferably both blades includes first and second spaced-apart electrodes which extend along the tissue contacting surface and are connectable to a voltage source, such as a high frequency bipolar RF power supply, for applying a voltage between the electrodes. As a result, current flows between the first and second electrodes of the blade to promote hemostasis in the tissue as the blade is moved into contact with tissue, such as during the cutting action.

In accordance with other aspects of the present invention, the first electrode of each of the blades may also define a shearing surface and a cutting edge of the blade. As in typical surgical scissors, the shearing surfaces of the blades are in a face-to-face relationship, but in accordance with the preferred aspects of the present invention, the first electrodes of each blade are of like polarity, so that there is no short circuiting between the shearing surfaces of the blades. Because the contacting shearing surfaces are of like polarity, there is no need to insulate the blades from one another, and a less complicated and less expensive scissor construction is required than in the prior patents discussed above. In accordance with this aspect of the present invention, the scissor shaft, which extends between the blades and an actuator handle, may itself be a conductor for connecting the first electrode of each blade to one terminal of a voltage source, and a single insulated conductor extending along the shaft may be used to connect the second electrode of each blade to the other terminal of the voltage source. Further, where the first electrode defines the cutting edge and shearing surface and also serves as the main structural element of each blade, relatively little force is exerted on the second electrode during cutting. As a result, a special high strength or high precision bonding process between the first and second electrodes is unnecessary, and less expensive bonding techniques should suffice.

In the above-described embodiment, the first and second electrodes preferably extend along a tissue contacting edge of the scissors, which is in proximity to the cutting edge. Accordingly, the current flow between the first and second electrodes serves to promote hemostasis in close proximity to the cut line, as the scissors are closed in a cutting action.

In accordance with another feature of the present invention, the first and second electrodes of each blade are located so that current not only flows between the first and second electrodes of each blade, but also between the first electrode of one blade and the second electrode of the other blade as the blades are brought into proximity during cutting. The flow of current between electrodes of different blades and electrodes of the same blade enhances coagulation and hemostasis during the cutting action.

In accordance with another aspect of the present invention, the scissors embodying the present invention may be used to promote coagulation during a blunt dissection or similar procedure, where the opening action of the scissors is used to contact or spread tissue. In this embodiment, each scissor blade has first and second spaced electrodes that extend along the rearward edge of the blades to contact tissue and promote coagulation as the blades are opened to spread or open tissue.

These and the many other features of the present invention, are set forth in the following detailed description of the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of electrosurgical scissors embodying the present invention.

FIG. 2 is a cross-sectional view of the distal end of the electrosurgical scissors of FIG. 1, depicting one means for attaching and moving the blades between open and closed positions, with the blades shown in an open position.

FIG. 3 is a longitudinal cross-sectional view of the distal end of the electrosurgical scissors of FIG. 2, taken along line 3—3 of FIG. 2, with the blades shown in a closed position.

FIGS. 4a-4 c are vertical cross-sectional views of one embodiment of scissor blades employing the present invention, taken along line 4—4 of FIG. 3, and showing the positions of the blades as they move from an open position in FIG. 4a in contact with the tissue to be cut, to an intermediate position in FIG. 4b just after the tissue is cut, and to a fully closed position in FIG. 4c.

FIGS. 5a-5 c are vertical cross-sectional views of another embodiment of scissor blades employing the present invention, showing the positions of the blades as they move from an open position in FIG. 5a in contact with the tissue to be cut, to an intermediate position in FIG. 5b just after the tissue is cut, and to a fully closed position in FIG. 5c.

FIGS. 6a-6 c are vertical cross-sectional views of a further embodiment of scissor blades employing the present invention, showing the positions of the blades as they move from an open position in FIG. 6a in contact with the tissue to be cut, to an intermediate position in FIG. 6b just after the tissue is cut, and to a fully closed position in FIG. 6c.

FIGS. 7a-7 c are vertical cross-sectional views of a further embodiment of scissor blades employing the present invention, showing the positions of the blades as they move from an open position in FIG. 7a in contact with the tissue to be cut, to an intermediate position in FIG. 7b just after the tissue is cut, and to a fully closed position in FIG. 7c.

FIG. 8 is a vertical cross-sectional view of one of the scissor blades of FIG. 6, showing how a single blade may be used to promote hemostasis in tissue.

FIGS. 9a-9 c are vertical cross-sectional views of the scissor blades of FIG. 5 showing the positions of the blades as they move from a closed position in FIG. 9a, to an intermediate position in FIG. 9b, to an open position in FIG. 9c, during a blunt dissection procedure.

FIG. 10 is a perspective view of an alternate embodiment of electrosurgical scissors embodying the present invention.

FIG. 11 is an exploded perspective view of the distal end of the electrosurgical scissors of FIG. 10 showing the blade members and associated structure.

FIG. 12 is an exploded perspective view of the proximal end of the electrosurgical scissors of FIG. 10 showing the handle and associated structure.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, the present invention is generally embodied in electrosurgical scissors, generally at 10, having a pair of scissor blades 12 joined for pivotal movement between open and closed positions. The present invention is not limited to any particular type or style of surgical scissors, and may be used in essentially any scissors that has a pair of movable blades. The particular scissors 10 shown in FIG. 1 is the type of scissors typically used in so-called minimally invasive or endoscopic surgery, where the scissor blades are inserted into the body cavity of a patient through a small diameter trocar.

In the scissors 10, the scissor blades are located at the distal of an elongated tubular shaft 14. As shown in FIGS. 2 and 3, the blades 12 are pivotally attached by pivot pin 16, which also attaches the blades to the distal end of shaft 14. A pair of linkages 18 connect the proximal ends of the blades to an actuator rod 20 that extends through the shaft. Axial movement of the actuator rod, which is controlled by handle 22 (FIG. 1) in a standard and well-known fashion, closes or opens the blades.

Alternatively, the proximal ends of the blades 12 may be slotted and the actuator rod 20 connected to a pin that slides within the slots, so that axial movement of the actuator rod opens and closes the blades. Examples of scissors employing a similar but somewhat more complicated structure than necessary in the present invention are described in U.S. Pat. Nos. 5,330,471 and 5,352,222, which are incorporated by reference herein.

In accordance with the present invention, as shown in FIG. 3, and in FIGS. 4-7, at least one blade, and preferably each blade of the scissors includes an inner conductive blade element 24 which defines a first electrode, an intermediate layer of insulative material 26 and an outer conductive blade element 28 which defines a second electrode. The inner blade element 24 includes a distal curved (or straight if desired) blade segment 30, which extends generally from pivot pin 16, and a proximal mounting segment 32 that is typically received within the end of shaft 14 and receives pivot pin 16 and linkages 18. Referring to FIG. 4a, each blade has a cutting edge 34, a shearing surface 36 and a tissue contact surface or edge 38 that extends along the cutting edge and contacts the tissue 40 as the blades close.

The inner blade element 24 is preferably metal, such as stainless steel, or other suitable material that is of high strength and will hold a sharp cutting edge for repeated use. As best seen in FIGS. 4-7, the inside surface of the inner blade element 24 forms the cutting edge 34 and shearing surface 36 of each blade. A forward surface 42 of the inner blade element extends along the cutting edge and the tissue contact surface for substantially the entire length of the blade segment 30.

Insulative material 26, separates the inner blade element 24 from the outer blade element 28. The insulative material may be made any suitable material that has sufficient resistance to electrically insulate the inner and outer blade elements. Preferably, the insulative material 26 also has sufficient bonding strength for bonding together the inner and outer blade elements. Because the outer blade element 28 does not include the shearing surface or cutting edge, the forces exerted on the outer blade element are limited, and the bond does not have to be as strong, for example, as employed in U.S. Pat. No. 5,352,222. It is believed that a relatively thin layer or film of insulation, such as the thickness of ordinary electrical tape, will provide sufficient insulation between the inner and outer blade elements. The spacing between inner and outer blade elements at the tissue contact surface is preferably between about 0.002 and 0.050 inches. Ordinary adhesives or materials that are suitable for bonding to metal in medical applications should suffice for bonding the inner and outer blade elements together. Alternatively, epoxy material, such as AF125 by 3M Company, as described in detail in U.S. Pat. No. 5,352,222, may be used to provide the insulative layer.

Outer blade element 28 is preferably a thin metal plate or strip, such as stainless steel or aluminum. Forward edge 44 of outer blade element 28 extends along the tissue contact surface 38, generally parallel to and spaced from the forward surface 42 of the inner blade element 24. As shown in longitudinal cross-section in FIG. 3, the insulating material 26 and outer blade element 28 preferably extend along the entire length of blade segment 30, including around the distal-most end of the blade segment.

The scissors of the present invention are preferably intended for connection to a voltage source, such as to the bipolar terminals of a commercially available bipolar RF energy generator. The bipolar RF generator may be connected to the scissors of the present invention at connectors 46 and 48 located near handle 22. Connector 46 is attached to an insulated conductor 50 that extends through shaft 14 and is connected at the distal end to each of the outer blade elements 28 of each blade. The other connector 48 is in electrical contact with the actuator rod 20 and shaft 14 which, in turn, are in electrical contact with the inner blade elements 24 of each blade via linkage 18 and pivot pin 16, respectively. Accordingly, the inner blade elements of each blade are attached to the same terminal of the voltage source and therefore have the same polarity. A standard insulating material such as plastic shrink tubing acts as a covering 45 along the outside surface of shaft 14, and protects surrounding tissue by preventing inadvertent conduction of electricity to or from the surface of the shaft. Alternatively, the shaft could be made entirely of insulative material, and electrical communication to the outer blade elements could be solely through the actuator rod, or vice versa.

FIGS. 4-7 show various possible blade configurations, in cross-section, as the blades close on tissue to be severed. Referring first to FIG. 4, FIG. 4a depicts the blades as they are closed and when they first come in contact the tissue 40 to be severed. Each blade has a shearing surface 36 and cutting edge 34. Each blade also includes an inside or forward tissue contacting edge surface 38. The inner blade element 24 forms the cutting edge and shearing surface of each blade. The inner blade also includes the forward edge or surface 42 that extends along the cutting edge for essentially the entire cutting length of the blade. The outer surface and back edge of the inner blade element are covered by insulative material 26. The insulative material 26 also extends beyond the back edge of inner blade element 24 to form an overhanging lip 52 of insulative material. This overhanging lip has a width approximately the same as or slightly greater than the width of the forward edge 42 of the inner blade element.

Outer blade element 28 extends along the tissue contacting edge surface 38 of the blade for substantially the entire length of the blade segment 30, and, as seen in cross-section, overlies only a portion of the outside surface of the inner blade element 24.

As shown by the arrows in FIG. 4a, when the tissue contacting edge or surface 38 of each blade comes into contact with the tissue 40 to be cut, current is believed to flow through the tissue between the inner blade element 24 and the outer blade element 28 of each blade, and as the blades come into proximity with each other, current flows through the tissue between the outer blade element 28 and inner blade element 24 of opposite blades. The current flow at the initial point of contacting the tissue is believed to be substantially between the inner and outer blade elements of the same blade along the tissue contacting edge. As the blades begin to cut the tissue and the distance between the blades decreases, the current flow between opposite electrodes of opposite blades increases.

FIG. 4b shows the blades in a position where the tissue has been severed, and the blades are not fully closed. At that position, it is understood that current flows substantially between the inner and outer blade elements of the same blade along the tissue contacting edge or surface 38, and may also flow between the outer blade element 28 and the shearing surface 36 of the inner blade element 24 of the other blade. The extent of current flow through the tissue in this situation may vary depending on the tissue type, position, thickness, and the extent to which the tissue is under tension.

FIG. 4c shows the blades in a fully closed position. At that position, the overhanging lip 52 of insulative material covers the forward edge 42 of the inner blade element 24 of the facing blade, essentially fully enclosing and insulating the inner blade elements 24 from tissue contact, and preventing current flow therethrough.

FIGS. 5a-5 c show an alternative embodiment of the present invention in which each of the blades similarly has a cutting edge 34, shearing surface 36, and tissue contacting edge or surface 38 for contacting tissue as the blades close. In addition, in this embodiment each of the blades includes a rearward edge or surface 54, which is displaced from or opposite the tissue contacting edge or surface 38, and which may be used for cauterizing tissue in those situations where it is desirable to cauterize tissue with the rearward surfaces of the blades.

More specifically, as shown in FIG. 5a, each blade includes the inner blade element 24, insulative material 26 over only the outside surface of the inner blade element, and outer blade element 28 which fully overlies the outside surface of the inner blade element. With this construction, as the tissue contacting edge of each blade comes into contact with tissue 40 for cutting, current is understood to flow between the surfaces 42 and 44 of the inner and outer elements of the same blade, and between the inner blade surface 42 and the outer blade surface 44 of opposite blades. As the blades are moved to a closed position, as shown in FIG. 5b, current is believed to flow between the outer blade surface 44 and the inner blade surface 42 of the same blade and between the inner blade element and outer blade element of the opposite blades. When the blades are fully closed, as shown in FIG. 5c, the forward and rearward surfaces 38 and 54 of the inner and outer electrodes of each blade are exposed, and current may continue to flow between the electrodes of each blade, when they are in contact with tissue.

The rearward edge of each blade in FIG. 5 has the same construction as the inside or forward edge of the blade, with tissue contacting surfaces 42′ and 44′ extending along the rearward surface 54, and therefore may be used for assisting in severing and promoting hemostasis of tissue that is contacted by the outside of the blades in a procedure such as blunt dissection. FIGS. 9a-9 c depict use of the scissors of FIG. 5 in a procedure such as a blunt dissection. A blunt dissection as depicted in FIG. 9 is where the scissors are inserted into the tissue in a closed or semiclosed position, and then opened to spread the tissue. Such a spreading action may result in bleeding from blood vessels ruptured during the procedure. In accordance with the present invention, the scissors of FIG. 5 may be used not only for promoting hemostasis during normal cutting but for promoting hemostasis during blunt dissection or the like.

FIG. 9a shows the scissor blades of FIG. 5 inserted into tissue 40 in a closed or near closed position. In this position, current flows through the tissue between surfaces 42 and 44 of the same blade at the inside tissue contacting surface and between surfaces 42′ and 44′ of the same blade at the rearward tissue contact surfaces. As the blades are moved to an intermediate position, the inside surfaces are no longer in close tissue contact and current flow between the inner and outer blade elements reduces or ceases. Current continues to flow through the tissue in contact with surfaces 42′ and 44′, promoting hemostasis in the tissue as the scissors spread. This current flow and hemostasis continues as the scissors fully open, as shown in FIG. 9c.

FIG. 6 shows another embodiment of the present invention, in which the inner blade element 24 is of essentially the same shape as that shown in FIG. 4, with the insulative layer 26 covering the same portion of the inner blade element as also shown in FIG. 4. In FIG. 6, however, the outer blade element 28 extends fully around the inner blade element to the same extent that the insulative material 26 extends around the material. The current flow between inner and outer elements of the blades in FIG. 6 is essentially the same as that described for FIG. 4. Also, similarly, when the blades are fully closed the inner blade elements 24 are essentially fully enclosed by the insulative material 26 and current flow between the inner and outer blade elements is effectively prevented. In this configuration, the outer electrode could be used as a monopolar electrode when the scissors are closed.

FIGS. 7a-7 c show yet another embodiment of the present invention similar to that of FIG. 6. In this embodiment, however, the inner blade element 24 tapers to a point at the tissue contacting edge or surface. In this embodiment, it is believed that the maximum amount of current flow will occur between the outer blade element of one blade and the inner blade element of the other blade as the blades sever the tissue. It should be noted that the wider the inner blade element surface 42 is, the more current will flow between electrodes (inner and outer elements) of the same blade, and the narrower the surface 42, the more current will flow between electrodes (inner and outer elements) of opposite blades. If the surface 42 width exceeds the typical current path length for bipolar energy (i.e., is greater than about 0.050 inches in width) then most of the current flow will occur between electrodes (inner and outer elements) of the same blade.

Finally, FIG. 8 depicts how the forward or tissue contact surface of a single blade embodying the present invention may be used to promote hemostasis independent of the tissue being severed.

Turning to FIGS. 10-12, there is seen a further embodiment of an endoscopic bipolar electrosurgical scissors in accordance with the present invention generally designated as 100. Like the embodiment described above, the scissors 100 comprises two inner conductive cutting blades 102, 104, each having an insulating member 106, 108, respectively, that is bonded to its blade member with a suitable adhesive. The insulating members 106, 108 each carry an outer electrode 110, 112, respectively.

The blades 102, 104, are joined together for pivotal movement to a two-part clevis 114 a, 114 b that is attached to the distal end of a conductive flexible tube member 116, the proximal end of which is secured to a handle 118 comprising two-parts 118 a, 118 b for controlling the opening, closing and electrical activation of the blades. The flexible tube 116 encases a flexible, helically-wound and coated wire tube 117 that is substantially coextensive with the tube 116. An insulative shrink fit tube 119 covers the tube 116 and the proximal portion of the blades 102, 104. In keeping with one aspect of the invention, improved means are provided for coupling the two outer electrodes 110, 112 to a voltage source of a first polarity and the two inner conductive cutting blades 102, 104 to a voltage source of a second polarity opposite to the first.

To conductively connect the outer electrodes 110, 112 to a voltage source of a first polarity, the handle includes an internal lug 120 in its proximal end that supports a first conductive contact 122. The lug 120 is maintained in position in the handle by means of a shim 123. The conductive contact 122 includes two arms 124 that are crimped to a conductive wire 126 that extends from the proximal end to the distal end of the handle. The distal end of the wire 126 is conductively connected to the proximal end of the flexible tube member 116 by means of a conductive connector 128 that is crimped to the wire 126 on one end and to a rigid member 130 on the other end that is press-fit into the proximal end of the conductive flexible tube member 116. The distal end of the flexible tube 116 has a conductive coupler 132 that secures the clevis 114 a, 114 b to the tube 116 by a crimp fit. An elongated conductive contact 134 is attached to the outer portion of each clevis half 114 a, 114 b.

The distal end of each conductive contact 134 extends slightly beyond the end of the clevis half to which it is attached so that it is in frictional or wiping contact with its associated outer electrode throughout the range of motion of the blade. Thus, when voltage of a first polarity is applied to the handle, it travels from the contact 122 through the wire 126 and connector 128 to the conductive tube 116. From the conductive tube 116, the voltage travels through the proximal end of the coupler 132, which conducts the voltage to the two contacts 134 which are conductively in contact with the inside surface of the coupler and, in turn, conduct the voltage to the outer electrodes 110, 112.

To conductively connect the inner conductive cutting blades 102, 104 to a voltage of a second polarity opposite to that applied to the outer electrodes 110, 112, the internal lug 120 in the handle supports a second conductive contact 136. The conductive contact 136 includes two arms 138 that are crimped to a second conductive wire 140 that extends from the proximal end of the handle to a pivotable thumb lever 142, which is discussed in greater detail below. The distal end of the wire 140 is secured to the thumb lever 142 by means of a conductive connector 144 that is crimped to the wire 140 on one end and to a conductive connector 146 on the other end that is press fit into a pivot connector 148 mounted to the lever 142. The connector 146 attaches to a conductive, flexible push rod 150, which is covered with an insulative shrink tube 151, that extends from the handle through the coated wire tube 117 to the blades 102, 104. A conductive clevis 152 is soldered to the distal end of the push rod 150 and supports a conductive pin 154 that is captured within obliquely-oriented slots 156 in the proximal portions of the inner conductive blades 102, 104. Thus, when a voltage of a second polarity is applied to the handle, it travels from the contact 136 through the wire 140, connector 144 and connector 146 to the lever 142. In the lever, the voltage travels from the connector 146 through the push rod 150 to the clevis 152 and pin 154, which contacts the inner conductive blades 102, 104.

To pivotally mount the blades 102, 104 to the clevis 114 a, 114 b and impart pivotal movement to the blades 102, 104, each blade includes an aperture 158 that receives an eyelet 160. The eyelet 160 extends between and interior of the clevis halves 114 a, 114 b. A rivet 162 whose shaft is received inside an insulating tube 164 extends between the exterior of the clevis halves 114 a, 114 b, thus pivotally securing the blade members 102, 104 together to the clevis halves 114 a, 114 b. The oblique slots 156 in the proximal ends of the blades create, in effect, lever arms to open and close the blades as the push rod pin 154 is moved back and forth.

Longitudinal motion is imparted to the push rod 150 by means of the back and forth movement of the thumb lever 142, the proximal end of the push rod 150 being secured to the pivot connector 148. The pivot connector 148 is, in turn, rotatably secured to an aperture in the lever 142 by a set screw 168. Thus, translational movement of the push rod 150 is provided by pivotal movement of the lever 142, with the pivot connector 148 rotating so that any sharing of force applied to the push rod 150 is minimized.

Although various alternative constructions for the electrosurgical scissors of the present invention are depicted, the present invention is not limited to these particular versions, and it is anticipated that other configurations may be used embodying the present invention which depart from the particular construction shown. 

What is claimed:
 1. An endoscopic surgical scissors including a pair of blades relatively moveable in a scissors-like action between open and closed positions, a handle operatively connected to the blades for effecting relative movement of the blades, the improvement comprising means for imparting pivotal movement to the blades including: a lever pivotally secured to the handle and moveable about a pivot axis between first and second positions, said lever including a generally cylindrical aperture having an axis generally parallel to and spaced from said pivot axis and a pivot connector rotatably received within said cylindrical aperture; a push rod having proximal and distal ends, the proximal end being secured to the pivot connector for axial movement upon the pivotal movement of the lever between first and second positions; a clevis attached to the distal end of the push rod and having a pair of spaced-apart arms; each blade having a proximal end containing an inclined slot, the slots being relatively obliquely oriented, and the proximal ends of the blades being received between the spaced-apart arms of the clevis; and a pin secured to the spaced-apart arms of the clevis and extending through the obliquely-oriented slots in the blades so that as the pin moves axially in response to axial movement of the push rod, the pin moves in the slots of the blades to pivot the blades between open and closed positions. 